lmkd: Implement watchdog thread
To detect lmkd being stuck on a syscall for prolonged period of time,
introduce a watchdog thread which gets set when lmkd starts handling of
events and is reset after handling is done. If it takes more than the
timeout period (2 sec) to handle an event, watchdog wakes up and kills
the least important process to prevent mounting memory pressure caused
by lmkd lockup. After a kill, watchdog will wait for the reset for
another timeout period and kill again. This repeats until lmkd unlocks
and resets the watchdog.
Bug: 201671997
Test: induce random sleep in lmkd main handler and observe watchdog kills
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I56a55834582e11c06cc6cf9da3bc7380e634b301
diff --git a/watchdog.cpp b/watchdog.cpp
new file mode 100644
index 0000000..b1e4a03
--- /dev/null
+++ b/watchdog.cpp
@@ -0,0 +1,123 @@
+/*
+ * Copyright 2021 Google, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "lowmemorykiller"
+
+#include <errno.h>
+#include <log/log.h>
+#include <string.h>
+
+#include <processgroup/processgroup.h>
+
+#include "watchdog.h"
+
+static void* watchdog_main(void* param) {
+ Watchdog *watchdog = static_cast<Watchdog*>(param);
+ sigset_t sigset;
+ int signum;
+
+ // Ensure the thread does not use little cores
+ if (!SetTaskProfiles(gettid(), {"CPUSET_SP_FOREGROUND"}, true)) {
+ ALOGE("Failed to assign cpuset to the watchdog thread");
+ }
+
+ if (!watchdog->create_timer(sigset)) {
+ ALOGE("Watchdog timer creation failed!");
+ return NULL;
+ }
+
+ while (true) {
+ if (sigwait(&sigset, &signum) == -1) {
+ ALOGE("sigwait failed: %s", strerror(errno));
+ }
+
+ watchdog->bite();
+ }
+
+ return NULL;
+}
+
+bool Watchdog::init() {
+ pthread_t thread;
+
+ if (pthread_create(&thread, NULL, watchdog_main, this)) {
+ ALOGE("pthread_create failed: %s", strerror(errno));
+ return false;
+ }
+ if (pthread_setname_np(thread, "lmkd_watchdog")) {
+ ALOGW("pthread_setname_np failed: %s", strerror(errno));
+ }
+
+ return true;
+}
+
+bool Watchdog::start() {
+ // Start the timer and keep it active until it's disarmed
+ struct itimerspec new_timer;
+
+ if (!timer_created_) {
+ return false;
+ }
+
+ new_timer.it_value.tv_sec = timeout_;
+ new_timer.it_value.tv_nsec = 0;
+ new_timer.it_interval.tv_sec = timeout_;
+ new_timer.it_interval.tv_nsec = 0;
+
+ if (timer_settime(timer_, 0, &new_timer, NULL)) {
+ ALOGE("timer_settime failed: %s", strerror(errno));
+ return false;
+ }
+
+ return true;
+}
+
+bool Watchdog::stop() {
+ struct itimerspec new_timer = {};
+
+ if (!timer_created_) {
+ return false;
+ }
+
+ if (timer_settime(timer_, 0, &new_timer, NULL)) {
+ ALOGE("timer_settime failed: %s", strerror(errno));
+ return false;
+ }
+
+ return true;
+}
+
+bool Watchdog::create_timer(sigset_t &sigset) {
+ struct sigevent sevent;
+
+ sigemptyset(&sigset);
+ sigaddset(&sigset, SIGALRM);
+ if (sigprocmask(SIG_BLOCK, &sigset, NULL)) {
+ ALOGE("sigprocmask failed: %s", strerror(errno));
+ return false;
+ }
+
+ sevent.sigev_notify = SIGEV_THREAD_ID;
+ sevent.sigev_notify_thread_id = gettid();
+ sevent.sigev_signo = SIGALRM;
+ if (timer_create(CLOCK_MONOTONIC, &sevent, &timer_)) {
+ ALOGE("timer_create failed: %s", strerror(errno));
+ return false;
+ }
+
+ timer_created_ = true;
+ return true;
+}